An image forming apparatus in which continuous paper sheets are used as a recording medium, for example, generally employs a stacker unit for stacking printed or copied sheets thereon. The stacker unit includes a table on which printed or copied sheets are stacked, and the table has the capability of stably stacking sheets and is constructed to be vertically movable for enabling the sheets accumulated on the table to be taken out of the apparatus.
In such an image forming apparatus, there is always the danger of pinching the operator's hand between the upper face of the table being lifted or the upper face of the sheets stacked on the table and the lower end of the front panel of the stacker unit or the peripheral devices, if the operator puts, by mistake, his hand in the interior of the stacker unit when the apparatus is in operation or if the operator presses, by mistake, a press button for lifting the table when he takes printed or copied sheets out of the stacker unit. For avoiding such an accident, conventional apparatus having such a stacker unit are provided with a safety bar mechanism at the lower end of the front panel of the stacker unit.
One example of prior art safety bar mechanisms is shown in FIGS. 11 and 12. This safety bar mechanism is disposed above a vertically movable table on which sheets are stacked and comprises a safety bar 103. The safety bar 103 has brackets 101,102 fixedly attached to both ends thereof and serves as a detector, taking the form of a bar bent at two points between the both ends. The brackets 101 and 102 are pierced to form holes 101a, 102a with their axes extending in the same direction as the longitudinal direction of the safety bar 103, and supporting shafts (not shown) attached to a fixed member are loosely inserted in these holes 101a, 102a. A micro switch 104 operated by either of the brackets (in this case, bracket 101) is disposed adjacently to the bracket 101. The micro switch 104 is electrically connected to a driver circuit for vertically moving the table.
With the above-described arrangement, the safety bar 103 is usually held at the position indicated by the two-dot chain line in FIG. 12 by its own weight and the micro switch 104 is accordingly pressed by the bracket 101 and turned ON. In this condition, in the event that the lower end of the safety bar 103 is touched by a hand or the like, the safety bar 103 will pivot on the two supporting shafts upwardly in a backward direction as indicated by the arrow in FIG. 12. The bracket 101 also pivots upwardly in a backward direction as indicated by the arrow in FIG. 12. This causes a lever 104a of the micro switch 104 to pivot to the position indicated by the solid line in FIG. 12, whereby the micro switch 104 is turned OFF and the rising table located under the safety bar 13 stops and then begins to lower. Thus, the accident of pinching the operator's hand between the table and the peripheral devices etc. can be avoided.